One type of the hybrid vehicle configured so that the engine and first and second motor generators (electric motors) are connected by a three-shaft power split device is disclosed for example in Japanese Patent Laying-Open No. 2007-131153 (PTL 1) and Japanese Patent Laying-Open No. 2003-247438 (PTL 2).
In a drive system of the hybrid vehicle having such a configuration, to a sun gear, a carrier, and a ring gear of a planetary gear train constituting the power split device, the crankshaft of the engine, the output shaft of the first motor generator, and the drive shaft are connected respectively. To the drive shaft, the output shaft of the second motor is further connected. The engine is started by being motored by the first motor generator (MG1). At this time, as the engine is motored, torque pulsation of the engine occurs. Vibration reduction control for suppressing this torque pulsation is disclosed in PTL 1.
According to PTL 1, based on the crank angle of the engine, a vibration reduction torque is set for suppressing the torque pulsation which occurs as the engine is motored. Then, to the output torque of the first motor generator (MG1) which generates a motoring torque for the engine, this vibration reduction torque is added, and accordingly the engine is started.
PTL 2 also discloses control for suppressing generation of gear's abnormal noise when the engine is started in a hybrid vehicle configured similarly to the above-described one. Specifically, PTL 2 discloses that the engine is cranked by the first motor generator (MG1) outputting a torque to which a pushing torque is added that is slightly greater than torque pulsation acting on the ring gear shaft due to torque pulsation of the engine. Thus, even if the engine is started while a lock mechanism (typically parking lock mechanism) is active that locks the drive shaft utilizing meshing of gears, noise due to impinging of the gears on each other can be prevented.